I am looking to display my iPad screen wirelessly to an external display to demo applications. I found this video showing exactly what I want to do with an iPhone but no explanation as to what the hardware dongle used was.
The main thing is that there isn't a wire tethering the user to the external display.

Just double-click the Home button, swipe all the way to the right, and select AirPlay Mirroring.– styfle Jan 12 '12 at 3:58